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Publikasjoner

NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.

2022

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Sammendrag

Historically, the autumn dynamics of deciduous forest trees have not been investigated in detail. However, autumn phenological events, like onset of loss of canopy greenness (OLCG), onset of foliar senescence (OFS) and cessation of wood growth (CWG), have an important impact on tree radial growth and the entire ecosystem's seasonal dynamics. Here, we monitored the leaf and wood phenological events of silver birch (Betula pendula) at four different sites in Ås, southeastern Norway: (a) a natural mature stand, (b) a plantation on former agricultural ground, (c) young natural trees, and (d) young trees in pots under different fertilization levels. The study took place over four consecutive years (from 2017 to 2020), with a particular focus on 2018, a year in which there was a severe summer drought, and the next year, 2019, which featured more normal conditions. First, we provided a description of birch phenology within its mid-north distributional. Second, we showed that drought advanced CWG by about 5 to 6 weeks and it delayed OLCG and OFS up to 30 days. Third, we observed an unexpected advance in OLCG in 2019 compared to 2018 (30 days) and 2020 (14 days). OFS presented similar dynamics as OLCG, whereas CWG was advanced only in 2018. These findings might indicate lag-effects of severe drought on the next year autumn leaf phenology but not on wood growth. On the other hand, the comparison between the natural stand and the plantation showed that, under drought conditions, wood growth is more sensitive to site fertility than autumn leaf phenology. In summary, our study elucidated the autumn dynamics of an important deciduous forest species in the northern temperate zone and showed unexpected impacts of a severely dry and warm summer on the current and next year leaf phenology.

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Sammendrag

The replacement of native birch with Norway spruce has been initiated in Norway to increase long-term carbon storage in forests. However, there is limited knowledge on the impacts that aboveground changes will have on the belowground microbiota. We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC). Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species-mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs. The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass.

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Sammendrag

Despite the increasing interest in applying composts as soil amendments worldwide, there is a lack of knowledge on short-term effects of compost amendments on soil structural and hydraulic properties. Our goal was to study the effect of compost and vermicompost-based soil amendments on soil structure, soil water retention characteristics, aggregate stability and plant water use efficiency compared to that of mineral fertilizers and food-waste digestate and examine if these effects are evident within a short time after application. We set up a pot experiment with spring wheat using a sandy and a loamy soil receiving either mineral fertilizer (MF); dewatered digestate from anaerobic digestion of food waste (DG), vermicomposted digestate (VC_DG); sewage sludge-based compost (C_SS) and sewage sludge-based vermicompost (VC_SS). We then monitored and calculated the soil water balance components (irrigation, outflow, evaporation, transpiration, and soil water content). At harvest, we measured shoot biomass, soil texture, bulk density, water retention characteristics and aggregate stability. The irrigation use efficiency (IE) and the plant water use efficiency (WUE) were calculated for each treatment by dividing the transpiration and the dry shoot biomass with the amount of water used for irrigation, respectively. For the sandy soil, we used X-Ray computed tomography to visualise the pore system after applying organic amendments and to derive metrics of the pore-network such as its fractal dimension, imaged macroporosity and critical pore diameter. X-Ray tomography indicated that composting and vermicomposting resulted in more complex and diverse porous system and increased soil macroporosity. The increased fractal dimensions also indicated that compost and vermicompost can contribute to structure formation and stabilization within a short time after their application. Despite the small application rate and short incubation time, the application of organic amendments to the two different soil types resulted in improved soil water holding capacity and water use efficiency. Composting and vermicomposting appeared to have the best effect at reducing the irrigation demand and evaporation losses and increasing the water use efficiency of the plant, likely through their effect on soil structure and the pore-size distribution.

Sammendrag

In a fertiliser experiment in a Norway spruce forest in SE Norway, four treatments were applied in a block design with three replicates per treatment. Treatments included 3 t wood ash ha−1 (Ash), 150 kg nitrogen ha−1 (N), wood ash and nitrogen combined (Ash + N), and unfertilised control (Ctrl). Treatment effects on understory plant species numbers, single abundances of species and (summarised) cover of main species groups were studied. Two years after treatment there were no significant changes for species numbers or abundances of woody species, dwarf shrubs or pteridophytes, nor for Sphagnum spp. in the bottom layer. The cover of graminoids decreased in Ctrl plots. Herb cover increased significantly in Ash + N and N plots due to the increase of Melampyrum sylvaticum. In Ash + N plots, mosses decreased significantly in species number, while their cover increased. Moss cover also decreased significantly in N plots. The species number and cover of hepatics decreased significantly in Ash and Ash + N plots. Hepatics cover also decreased in Ctrl plots. Both the lichen number and cover decreased in Ash + N plots. Single species abundances decreased for many bryophytes in fertilised plots. To conclude, fertilisation had modest effects on vascular plants, while bryophytes were more strongly affected, especially by Ash + N.